Moderate dose of watercress and red radish does not reduce oxygen consumption during graded exhaustive exercise

Very recent studies have reported positive effects of dietary nitrate on the oxygen consumption during exercise. This research aimed to study the effect of moderate dose of high-nitrate vegetables, watercress (Nasturtium officinale) and red radish (Raphanus sativus) compared with a control group on the incremental treadmill exercise test following a standard Bruce protocol controlled by computer. Group 1 consumed 100 g watercress (n=11, 109.5 mg nitrate/day), and group 2 consumed 100 g red radish (n=11, mg 173.2 mg nitrate/day) for seven days, and control group (n=14) was prohibited from high nitrate intake. During exercise, watercress group showed significant changes in the maximum values of Respiratory Exchange Ratio (RER) (p<0.05), End-Tidal O2 Fraction (FETO2) (p<0.05), and energy consumption from carbohydrate (p<0.01). Red radish group had a significant increase in the VCO2 (p<0.01), RER (p<0.01), VT (p<0.05), VCO2/kg (p<0.05), and energy consumption from carbohydrates (p<0.01). When all groups in the same workload were normalized by the subject’s body mass, watercress had a significant increase in the total expired CO2 (p<0.05), RER (p<0.05), FETO2 (p<0.05), and energy consumption from carbohydrates (p<0.05) compared with the control group. Similar comparison between red radish and control group revealed a significant increase during pre-test in the total CO2 production (p<0.05), VCO2 (p<0.05), RER (p<0.01), VT (p<0.05), and VCO2/kg (p<0.05). Current results indicate higher carbon dioxide production in the experimental groups in the same workload. This might have a negative impact on the exercise performance. Further investigations with controlled exercise program will be necessary.